The advent of the Internet has increased the demand for email and other electronic messaging services. Most Internet service providers (ISPs) offer email accounts automatically when a new user is registered. In terms of Internet email transport, the overall client/server protocol employed for transmitting email messages is the Simple Mail Transfer Protocol (SMTP). The host mail server run by the typical ISP includes an SMTP server, which handles email by managing queues and reconciling addresses. Most ISPs offer consumer Internet accounts based on dial-up (PPP) protocols. Under this protocol the consumer client, operating a personal computer or other device, uploads mail to the host email server using SMTP and downloads mail using the Post Office Protocol, presently version 3 (POP3). The typical architecture is illustrated in FIG. 1. POP3 is a low-overhead protocol for general download service, offering the ability to perform basic operations such as listing and deleting email messages.
However, deploying POP3 for email access entails disadvantages. One is that the client's personal computer must be programmed to know the precise address of the root email mailbox, by identifying the IP address of the host mail server. If the account holder's mailbox is moved to a different host mail server at a different IP address, the software on the client's personal computer must be reprogrammed to reflect the new destination. As a result, ISPs are reluctant to move account holder mailboxes, and can only do so with great attention. This limits the flexibility of ISPs in deploying new mail hosting technologies, including to change or upgrade mail servers.
Another disadvantage of the POP3 architecture is that if an account holder chooses to change ISPs entirely, there is in general no mechanism to transfer the account holder's email mailbox to the new service provider, intact. There is, moreover, no provision for the coexistence of two mailboxes with the same account name but different mail server hosts. Thus, a consumer who has changed ISPs must periodically check both the old email mailbox and the new mailbox until the transition is complete. Similarly, when an account holder maintains both a business email address and a personal email address, they must access each of those mailboxes separately.
Moreover, on the server side, ISPs need to maintain their host mail servers with modules to register and process billing information, account statistics and other value-added services. There are no industry standards for those mail server services, and they vary from one ISP to the next. Consequently, individual ISPs are effectively locked into a single vendor's package to maintain attendant services at the level of the mail server, or be forced to write conversion software when a new service package is introduced, so as not to disrupt the addressing scheme for their customers. Other problems exist.